1. Field of the Invention
Spent potlinings are carbonaceous products resulting from the demolition of the lining of the walls and bottom of the electrolytic pots which constitutes the cathode. This lining wears out and deteriorates and it is necessary to replace it periodically by a new lining. The lining-demolition operation, called unlining, is carried out by means of pneumatic tools and gives large-size lumps which may contain inclusions of metals such as iron and aluminium. Next, these lumps are reduced, by conventional means, to a size allowing them to go through a more or less 400 mm square-mesh grate.
2. Description of the Prior Art
Spent potlinings are strongly impregnated with noxious products, fluorides and cyanides for example. Up to now, they have been tipped in waste dumps, but the new regulations about pollution and environmental protection make it an obligation to treat them, e.g. to calcine them, in order to eliminate the noxious products and, possibly, to recover carbonaceous constituents.
The invention relates more particularly to the aluminium smelters in which the spent potlinings must be reduced into pieces not bigger than a few millimetres in size before being treated, and is concerned with a process and a grinding plant permitting to reach this result with only two size reduction stages and a screening operation.